#include<iostream>
using namespace std;

int main()
{
	int n;
	cin >> n;
	
	int arr[n];
	for (int i = 0; i < n; i++)
		cin >> arr[i];
	
	int x;
	cin >> x;
	
	int i = 0;
	for (i = 0; i < n; i++)
		if (arr[i] == x)
		{
			cout << i << endl;
			break;
		}
		
	if (i == n)
		cout << -1 << endl;
	
	return 0;
}
